Distribution of Fc and complement receptors in spleen sections. I. Comparison of various erythrocyte indicator systems

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Hemadsorption patterns on cryo-sections of normal human spleen incubated with sheep, bovine and chicken erythrocytes (E) coated with rabbit IgG (EAG) or IgM (EAM) antibodies, or IgM antibodies and mouse complement (EAMC mo) or rabbit complement (EAMC ra) were studied. No hemadsorption was seen with unsensitized E of the three species. Sheep, bovine and chicken EAG reacted with red pulp, bovine EAG most strongly. Heavily coated bovine EAG also reacted with the white pulp. White pulp but not red pulp EAG hemadsorption was decreased at 4°C. EAG red pulp hemadsorption was stable for several hours at 4 to 37°C, was not markedly affected by EDTA or by trypsin treatment of the sections, but was completely inhibited by native or heat aggregated human IgG and staphylococcal protein A; it was also sensitive to heating above 65°C and to fixation with formalin and glutaraldehyde. The characteristics of EAG red pulp hemadsorption are compatible with a reaction mediated by an Fc receptor for IgG. Sheep, bovine and chicken EAMC mo and EAMC ra reacted with white pulp areas. The EAMC mo gave the strongest white pulp hemadsorption reaction, particularly with sheep E. Sheep but not bovine or chicken, EAMC ra reacted weakly with red pulp. EAMC white pulp hemadsorption was abolished by mild trypsin treatment or fixation of the sections. The characteristics of the EAMC white and red pulp hemadsorption are compatible with a reaction mediated by complement receptors. The results suggest that C3b receptors are present in both white and red pulp and that C3d receptors are restricted to white pulp. The use of these indicator systems for demonstrating Fc and complement receptors in malignant lymphomas is suggested.